email body content is sent as an attachments(ATT00001.htm)

When sending the mail using chilkat.net Mailman, The email body content is sent as an attachments(ATT00001.htm) . On analysis it is due to Microsoft exchange server issue which convert the body content to attachment only when the email has any attachments.

As per the below solution the body content should be set as First before the attachments(hope so in mime file). https://support.microsoft.com/en-gb/help/969854/the-body-of-a-message-is-shown-incorrectly-as-an-attachment-if-you-try-to-use-an-application-in-an-exchange-server-environment-to-send-a-message-that-includes-attachments

below is the .net code used to send the mail.

Email.AddFileAttachment(ImagePath) Email.SetHtmlBody(Htmlcontent) Mailman.SendEmail(Email);

how to achieve this or any other solution to avoid the body content as attachments.

Thanks in Advance Rajesh